STRUCTURAL CHARACTERIZATION OF THE GALACTOXYLOMANNAN OF CRYPTOCOCCUS-NEOFORMANS CAP67

The galactoxylomannan (GalXM) obtained from the culture supernatant of an acapsular mutant of Cryptococcus neoformans Cap67 was purified by Concanavalin A affinity, ion-exchange, and gel-filtration chromatograp hies. The structure of GalXM was determined by methylation analysis an d by 1D and 2D NMR spectroscopic studies of the intact polysaccharide and of the oligosaccharide fragments generated by Smith degradation an d by acetolysis. GalXM is a complex polysaccharide with an alpha-(1 -- > 6)-galactan backbone. The polysaccharide is branched at C-3 of alter nate Gal units of the backbone. C-3 is the point of attachment of the oligosaccharide side chains comprised of alpha-D-Man-(1 --> 3)-alpha-D -Man-(1 --> 4)-beta-D-Gal-substituted with zero to three terminal beta -Xyl residues as shown in the following structure: GRAPHICS (C) 1998 E lsevier Science Ltd. All rights reserved.